134 



THE TISSUES 



it to the Nissl technic, we note that the cytoplasm is composed of 

 two distinct elements: (a) a clear, unstained ground substance, and, 

 scattered through this, (b) deep-blue-staining masses, the chromo- 

 philic bodies (Fig. 75), These bodies are granular in character and 



differ in shape, size, and arrangement. 

 They may be large or small, regular or 

 irregular in shape, may be arranged in 

 rows or in an irregular manner, may be 

 close together, almost filling the cell body, 

 or quite separated from one another. 

 Presenting these variations in different 

 types of cells, the appearance of the 

 chromophilic bodies in a particular type 

 of cell remains constant, and has thus been 

 used by Nissl as a basis of classification.^ 

 It is important to note in studying the 

 nerve cell by this method that somato- 

 chrome cells of the same type frequently 

 show marked variations in staining in- 

 tensity. This appears to depend upon 

 the size and closeness of arrangement of 

 the chromophiHc bodies, and this again 

 seems dependent upon changes in the 

 cytoplasm connected with functional 

 activity. 



In cells stained by Nissl's method the 

 cytoplasm between the chromophilic 

 bodies remains unstained and apparently 

 structureless, and it is this part of the 

 cytoplasm that corresponds to the neuro- 

 fibrils and a part at least of the perifibril- 

 lar substance. 



Fig. 78.— Pyramidal CeU 

 from Human Cerebral Cortex. 

 (Golgi bichlorid method. See 

 2, p. 36.) Golgi cell type I. 

 fl, Cell body; b, main or apical 

 dendrite showing gemmules; 

 c, lateral dendrites showing 

 gemmules; d, axone with col- 

 laterals. Only part of axone 

 is included in drawing. 



The relation which the appearance of the Nissl-stained cell bears to the 

 structure of the living protoplasm is still undetermined. According to some 

 investigators the Nissl bodies exist as such in the living cell. Others believe 

 that they are not present in the living cell, but represent precipitates due 

 either to postmortem changes or to the action of fixatives. The significance 

 of the Nissl picture from the standpoint of pathology lies in the fact that 

 when subjected to a given technic, a particular type of nerve cell always pre- 



^ For this classi&cation, the significance of which is somewhat doubtful, the reader 

 is referred to Barker, "The Nervous System and Its Constituent Neurones," p. 121. 



